Mealybug Destroyers
Answered by: Inge Poot
Question from: Sarah Hogarth
Posted on: December 30, 2008

I work at a retail greenhouse in London, Ontario. We keep about an acre and a half of greenhouse operational year-round. A couple of months ago, we introduced about 600 mealybug destroyer insects to help control our severe mealybug and aphid problem (at a cost of somewhere around $500 - 600). The MB destroyer population is starting to establish itself, and they are reproducing and multiplying well; however, given the severity of our pest problem, I understand that it will take several more months before we really see the mealybug and aphid populations being brought under control. Unfortunately, the greenhouse manager is not as patient as I am, and despite my attempts to persuade him otherwise, plans to douse the whole greenhouse with Cygon while we’re closed over the holidays.

My question is this: if I were to gather up as many of the MB destroyer adults and larvae as I can find over the next day or two, could they be stored in some way for a couple of weeks to be reintroduced into the greenhouse later? Could I keep them in paper bags with rafia/irish moss in a cooler? What are the minimum temperatures that they’d withstand? Would the residual effects of the Cygon wind up killing them in the end anyway?

Mealybug destroyers are a type of ladybug and I think the adults would survive just fine in a fridge, provided they are kept moist and if some sugar water is added to the packing medium they are kept in. I am not at all sure that the larvae would survive, but it would not hurt to try.

The Cygon has a systemic action that lasts 6 weeks and I am not sure that the MB destroyers would survive there if re-introduced after two weeks. I think that batch is a write off.

However, maybe you could convince your boss to use neem oil or even enstar in the future, since they would be far less dangerous to the people coming in contact with the plants after treatment. Both the neem oil and the enstar work especially well for aphids. For the mealybugs several applications will be needed and after that you could safely re-introduce new batches of the mealybug destroyers periodically. They would then prevent such an explosive multiplication of any left-over or resistant pests in the future. If you do not have many pests to start with you will not get the rapid and abundant reproduction of the predators. In the end, by not using the Cygon, they would have been there in such numbers that they eradicated the pests. But by using the poison, your boss made that impossible.

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